Exchange for changing a route of a transmission path to bypass a malfunctioning switch

ABSTRACT

An exchange changes a route of a transmission path to bypass a malfunctioning switch. The transmission path is formed in a switch network including a plurality of switches for transmitting communication information. The switch network is provided with a plurality of inputs and a plurality of outputs so that the transmission path is formed between one of the inputs and one of the outputs by routing the switches in the switch network. A malfunctioning switch detecting unit detects a location of the malfunctioning switch in the switch network. The route of the transmission path is changed by switching one of the inputs and outputs connected to the transmission path based on predetermined routing information which indicates a route to bypass the malfunctioning switch in relation to the inputs or the outputs of the switch network.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to an exchange and, moreparticularly, to an exchange which changes a route of a transmissionpath, when a malfunction occurs in one of a plurality of switches, so asto bypass the malfunctioning switch.

[0003] In an exchange or a transmission apparatus which communicatesinformation including audio data and image data, a switch network isprovided with a plurality of inputs and outputs so that any one of theinputs can be connected to any one of the outputs so as to arbitrarilychange a route of a communication path formed in the switch network.

[0004] 2. Description of the Related Art

[0005] A description will now be given of a conventional method foravoiding influence of a malfunction occurring in one of a plurality ofswitches which constitute a switch network in an exchange.

[0006]FIGS. 1, 2 and 3 show a first, second and third conventionalexchange, respectively.

[0007] The first conventional exchange shown in FIG. 1 comprises aworking switch network 101, a spare switch network 102 having the samestructure as the working switch network 101, an input switching unit 103and an output switching unit 104. The working switch network 101comprises a plurality of switches, and has a plurality of inputs and aplurality of outputs. The input switching unit 103 and the outputswitching unit 104 change a transmission path formed through theexchange so that the transmission path is formed in the spare switchnetwork 102 instead of the working switch network 101 when a malfunctionoccurs in one of the switches in the working switch network 101 which isactually being used.

[0008] When a malfunction occurs in one of the switches constituting theworking switch network 101, the first conventional exchange bypasses themalfunctioning switch by switching the actually used switch network fromthe working switch network 101 to the spare switch network 102. Thisswitching operation is performed by the input switching unit 103 and theoutput switching unit 104. Transmission paths formed after the switchingoperation are also formed in the spare switch network 102.

[0009] The second conventional exchange shown in FIG. 2 comprises aswitch network 111, an input switching unit 112, an output switchingunit 113 and a header changing table circuit 114. The switch network 111comprises a plurality of switches and a plurality of spare switchesreserved for spare use. The switch network 111 has a plurality of inputsand a plurality of outputs, and also has a plurality of spare inputs anda plurality of spare outputs. The input switching unit 112 and theoutput switching unit 113 change a route of a transmission path formedthrough the exchange so that the transmission path is formed between oneof the spare inputs and one of the spare outputs when a malfunctionoccurs in one of the switches included in the transmission path in theswitch network. The header changing table circuit 114 changes inputaddress information, which is included in communication information tobe transmitted, to input address information of one of the spare inputs.

[0010] When a malfunction occurs in one of the switches in the switchnetwork 111, the second conventional exchange bypasses themalfunctioning switch by changing a route of the transmission pathincluding the malfunctioning switch to a route formed between one of thespare switches and one of the spare inputs.

[0011] The third conventional exchange shown in FIG. 3 comprises aswitch network 121 including a plurality of switches. The switch network121 has a plurality of inputs and a plurality of outputs. When amalfunction occurs in one of the switches constituting the switchnetwork 121, the malfunctioning switch is detected so that atransmission path routing the malfunctioning switch is changed to atransmission path routing a spare switch instead of the malfunctioningswitch.

[0012] However, each of the above-mentioned conventional exchanges hasthe following problems.

[0013] In the first conventional exchange, since a detection of themalfunctioning switch in the actually used working switch network 101 isnot performed, a transmission path routing the malfunctioning switchcannot be distinguished. Thus, all transmission paths including normaltransmission paths must be switched to transmission paths formed in thespare switch network 102 when a malfunction occurs in one of theswitches in the working switch network 101.

[0014] In the first, second and third conventional exchanges, since thespare switch network or the spare switch must be reserved for spare usewhich is not used in a normal condition, weight and size of the entiresystem is increased and also manufacturing cost of the exchange isincreased.

SUMMARY OF THE INVENTION

[0015] It is a general object of the present invention to provide anexchange in which the above-mentioned problems are eliminated.

[0016] A more specific object of the present invention is to provide anexchange in which, when a malfunction occurs in one of a plurality ofswitches, a transmission path bypassing the malfunctioning switch can beformed in the absence of a spare switch in the exchange so as todecrease weight and size of the entire system.

[0017] In order to achieve the above-mentioned objects, there isprovided according to the present invention an exchange setting atransmission path for transmitting communication information through aswitch network comprising a plurality of switches, the switch networkprovided with a plurality of inputs and a plurality of outputs so thatthe transmission path is formed between one of the inputs and one of theoutputs by routing the switches in the switch network, the exchangechanging a route of the transmission path when a malfunction occurs inone of the switches included in the transmission path so as to bypassthe malfunctioning switch, the exchange comprising:

[0018] a malfunctioning switch detecting unit detecting a location ofthe malfunctioning switch in the switch network; and

[0019] changing means for changing the route of the transmission path byswitching one of the inputs and outputs connected to the transmissionpath based on predetermined routing information so as to bypass themalfunctioning switch.

[0020] According to the above-mentioned invention, when a malfunctionoccurs in one of the switches constituting the switch network, thelocation of the malfunctioning switch is detected and the locationinformation is supplied to the changing means. The location informationmay include an address of the malfunctioning switch and informationindicating a position of the malfunctioning switch with respect to theinputs and outputs of the switch network. For example, if the switchesin the switch network are arranged in a matrix, the location informationmay include indication of a column (stage) in which the malfunctioningswitch is included. When the changing means receives the locationinformation, the changing means changes the route of the transmissionpath by changing one of the inputs which is connected to thetransmission path or changing one of the outputs connected to thetransmission path. That is, the input or the output connected to thetransmission path is changed to another input or output based on therouting information which indicates a route which bypasses themalfunctioning switch. That is, the route of the transmission path canbe changed to a route which bypasses the malfunctioning switch by merelychanging the input or output of the switch network.

[0021] Accordingly, the exchange according to the present inventiondiscriminate the transmission path including the malfunctioning switch,and the route of the transmission path is changed by changing the inputor the output of the switch network based on the location of themalfunctioning switch. Thus, the exchange according to the presentinvention does not need a spare switch which is not used when theexchange is operated in a normal condition. Therefore, the weight andsize of the entire system is reduced which is advantageous for reducingmanufacturing cost.

[0022] In the exchange according to the present invention, the changingmeans may comprise:

[0023] a storing unit which stores table information indicating aplurality of routes each of which bypasses one of the switches in theswitch network, each of the routes being indicated in relation to one ofthe inputs and outputs of the switch network; and

[0024] a selecting unit selecting one of the routes indicated in thetable information so as to change the route of the transmission path tobypass the malfunctioning switch.

[0025] Accordingly, if the location of the malfunctioning switch isdetected, a route which bypasses the malfunctioning switch can beobtained from the table information in relation to the input or theoutput of the switch network.

[0026] In one embodiment according to the present invention, thechanging means may comprise:

[0027] an input switching unit switching the input of the switchnetwork;

[0028] an output switching means switching the output of the switchnetwork; and

[0029] input and output selecting means for selecting one of the inputswitching unit and the output switching unit so that the changing meanschanges the route of the transmission path by the selected one of theinput switching unit and the output switching unit.

[0030] The input and output selecting means may select the inputswitching unit when the malfunctioning switch is one of the switchesdirectly connected to the input switching unit. Additionally, the inputand output selecting means may select the output switching unit when themalfunctioning switch is one of the switches directly connected to theoutput switching unit.

[0031] Additionally, the input and output selecting means may select theinput switching unit when the malfunctioning switch is one of theswitches other than the switches directly connected to one of the inputswitching unit and the output switching unit. Alternately, the input andoutput selecting means selects the output switching unit when themalfunctioning switch is one of the switches other than the switchesdirectly connected to one of the input switching unit and the outputswitching unit.

[0032] Other objects, features and advantages of the present inventionwill become more apparent from the following detailed description whenread in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a block diagram of a first conventional exchange;

[0034]FIG. 2 is a block diagram of a second conventional exchange;

[0035]FIG. 3 is a block diagram of a third conventional exchange;

[0036]FIG. 4 is a block diagram of an exchange according a firstembodiment of the present invention:

[0037]FIG. 5 is a block diagram of a control unit shown in FIG. 4;

[0038]FIG. 6A is an illustration of a switch network for explaining anoperation of the control unit when a malfunction occurs in a switchincluded in a first stage;

[0039]FIG. 6B is an illustration for explaining input table (1)information;

[0040]FIG. 6C is an illustration for explaining each switch included inthe switch network shown in FIG. 4;

[0041]FIG. 7A is an illustration of the switch network for explaining anoperation of the control unit when a malfunction occurs in a switchincluded in a final stage;

[0042]FIG. 7B is an illustration for explaining output table (1)information;

[0043]FIG. 8A is an illustration of the switch network for explaining anoperation of the control unit when a malfunction occurs in a switchincluded in an intermediate stage;

[0044]FIG. 8B is an illustration for explaining input table (2)information;

[0045]FIG. 9A is an illustration of the switch network for explaining anoperation of the control unit when a malfunction occurs in a switchincluded in the intermediate stage;

[0046]FIG. 9B is an illustration for explaining output table (2)information;

[0047]FIG. 10 is a block diagram of an input switching unit shown inFIG. 4;

[0048]FIG. 11 is a block diagram of an output switching unit shown inFIG. 4;

[0049]FIG. 12A is an illustration for explaining an operation of aninput switching unit shown in FIG. 10 when a malfunction occurs in oneof the switches in the first stage;

[0050]FIG. 12B is an illustration for explaining an operation of anoutput switching unit shown in FIG. 11 when a malfunction occurs in oneof the switches in the first stage;

[0051]FIG. 13A is an illustration for explaining an operation of aninput switching unit shown in FIG. 10 when a malfunction occurs in oneof the switches in the final stage;

[0052]FIG. 13B is an illustration for explaining an operation of anoutput switching unit shown in FIG. 11 when a malfunction occurs in oneof the switches in the final stage;

[0053]FIG. 14 is a flowchart of an operation of the exchange shown inFIG. 4;

[0054]FIG. 15A is an illustration for explaining a transmission pathformed in the switch network before a change is made to the transmissionpath when a malfunction occurs in one of the switches in the firststage;

[0055]FIG. 15B is an illustration for explaining the transmission pathof FIG. 15A after the change;

[0056]FIG. 16A is an illustration for explaining a transmission pathformed in the switch network before a change is made to the transmissionpath when a malfunction occurs in one of the switches in the finalstage;

[0057]FIG. 16B is an illustration for explaining the transmission pathof FIG. 15A after the change;

[0058]FIG. 17A is an illustration for explaining a transmission pathformed in the switch network before a change is made to the transmissionpath when a malfunction occurs in one of the switches in theintermediate stage;

[0059]FIG. 17B is an illustration for explaining the transmission pathof FIG. 15A after the change; and

[0060]FIG. 18A is an illustration for explaining a transmission pathformed in the switch network before a change is made to the transmissionpath when a malfunction occurs in one of the switches in the firststage;

[0061]FIG. 18B is an illustration for explaining the transmission pathof FIG. 15A after the change.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] A description will now be given of an exchange according to afirst embodiment of the present invention.

[0063]FIG. 4 is a block diagram of the exchange according to the firstembodiment of the present invention. The exchange shown in FIG. 4comprises a switch network 1, a control unit 2, an input switching unit3 and an output switching unit 4. When a malfunction occurs in one of aplurality of switches in the switch network 1, the exchange switches atransmission path so as to bypass the malfunctioning switch.

[0064] The switch network 1 of the present embodiment comprises twelve(12) switches each having two (2) inputs and two (2) outputs so as toconstitute a switch network having eight (8) inputs and eight (8)outputs. For example, the eight (8) inputs of the switch network 1 areprovided with eight (8) input addresses from “000” to “111”, and eight(8) outputs are provided with eight (8) output addresses from “000” to“111”. In the switch network 1, the switches are arranged in a 3×4matrix. Four (4) switches in the first stage (first column) areconnected to the inputs of the switch network 1. The first stage isreferred to as a malfunction stage (a). Four (4) switches in the finalstage (third column) are connected to the outputs of the switch network1. The final stage is referred to as a malfunction stage (c). Four (4)switches in the intermediate stage (second column) are not connectedwith either the inputs or the outputs. The intermediate stage is definedas a malfunction stage (b). Additionally, the switches in the first row(the uppermost row) are given a switch address “00”; the switches in thesecond row are given a switch address “01”; the switches in the thirdrow are given a switch address “10”; the switches in the fourth row (thelowermost row) are given a switch address “11”.

[0065] The switch network 1 has a function to change a route of atransmission path formed in the switch network 1 based on predeterminedrouting information of a previously set route and location informationof a malfunctioning switch. Although the switch network 1 of the presentembodiment comprises twelve (12) switches and has eight (8) inputs andeight (8) outputs, the number of switches, the number of inputs and thenumber of outputs are not limited to those numbers.

[0066] The control unit 2 serves as a changing means for changing aroute of a transmission path formed in the switch network 1. That is,when a malfunction occurs in the switch network 1, the control unit 2sets a final stage malfunction flag and produces input and output unitchanging information. The final stage malfunction flag is set forselecting one of the ways to bypass the malfunctioning switch by eitherchanging the input address or output address. The selection by thecontroller is performed based on address information of themalfunctioning switch and information of the malfunction stage in whichthe malfunction switch is included. The input and output unit changinginformation is used for changing a transmission path in the switchnetwork 1 so as to bypass the malfunctioning switch.

[0067] The input switching unit 3 serves as an input switching means ofthe changing means. That is, when a malfunction occurs in the switchnetwork 1, the input switching unit 3 switches a path to the inputs ofthe switch network 1 based on the input and output unit changinginformation produced by the control unit 2.

[0068] The output switching unit 4 serves as an output switching meansof the changing means. That is, when a malfunction occurs in the switchnetwork 1, the input switching unit 3 switches a path from the outputsof the switch network 1 based on the final stage malfunction flag set bythe control unit 2.

[0069] A description will now be given, with reference to FIG. 5, of thecontrol unit 2 shown in FIG. 4 in more detail.

[0070] As shown in FIG. 5, the control unit 2 comprises a malfunctioningswitch detecting unit 5, an input and output table storing unit 6, aninput table (1) storing unit 7, an output table (1) storing unit 10, aselecting unit 11 and a final stage flag producing unit 12.

[0071] The malfunctioning switch detecting unit 5 serves as adiscriminating means for discriminating a switch in which a malfunctionoccurs. That is, when a malfunction occurs in one of the switches in theswitch network 1, the malfunctioning switch detecting unit 5 detects themalfunctioning switch.

[0072] The input table (1) storing unit 7 serves as a storing means forstoring an input table (1) information as predetermined routinginformation. The input table (1) information is referred to when themalfunctioning switch is included in the malfunction stage (a) (thefirst stage) of the switch network 1 so as to change a transmission pathto bypass the malfunctioning switch. That is, the input table (1)storing unit 7 stores the input table (1) information which indicateseach switch in the switch network 1 in relation to transmission pathseach of which bypasses each switch in the switch network 1.

[0073] The output table (1) storing unit 10 serves as a storing meansfor storing an output table (1) information as predetermined routinginformation. The output table (1) information is referred to when themalfunctioning switch is included in the malfunction stage (c) (thefinal stage) of the switch network 1 so as to change a transmission pathto bypass the malfunctioning switch. That is, the output table (1)storing unit 10 stores the output table (1) information which indicateseach switch in the switch network 1 in relation to transmission pathseach of which bypasses each switch in the switch network 1.

[0074] The input and output table storing unit 6, which serves as astoring means, comprises at least one of an input table (2) informationstoring unit 8 for storing an input table (2) information and an outputtable (2) information storing unit 9 for storing an output table (2)information. The input table (2) information or the output table (2)information is referred to when a malfunctioning switch is included inthe malfunction stage (b) (the intermediate stage). The input table (2)information and the output table (2) information serves a functionsimilar to the input table (1) information and the output table (1)information.

[0075] The selecting unit 11 serves as a path selecting means forselecting a transmission path which bypasses a malfunctioning switch.That is, when a malfunction occurs in one of the switches in the switchnetwork 1, the selecting unit 11 selects a transmission path whichbypasses the malfunctioning switch based on the input table (1)information, the output table (1) information, the input table (2)information and the output table (2) information.

[0076] The final stage malfunction flag producing unit 12 sends anotification to the input switching unit 3 so as to set the final stagemalfunction flag to “ON” when switching is performed by the outputswitching unit 4.

[0077] A description will now be given, with reference to FIGS. 6A, 6Band 6C, of an operation of the control unit 2 when the input table (1)information stored in the input table (1) storing unit 7 is referred to.

[0078]FIG. 6A shows a case in which a malfunction occurs in a switchhaving a switch address “00” in the malfunction stage (a). In the caseshown in FIG. 6A, an original routing information is “000111” whichindicates a transmission path routing from the input having the address“000” to the output having the address “111” (indicated by a bold solidline in FIG. 6A). Each of the switches constituting the switch network 1has a 0-input terminal, a 0-output terminal, a 1-input terminal and a1-output terminal as shown in FIG. 6C. The input address “000” indicatesthe input terminals of the malfunction stages (a), (b) and (c),respectively. The output address “111” indicates the output terminals ofthe malfunction stages (a), (b) and (c), respectively. Accordingly,communication information input to the input address “000” of the switchnetwork 1 is first input to the 0-input terminal of the switch havingthe switch address “00” in the malfunction stage (a), and output fromthe 1-output terminal of the same switch. Then, the communicationinformation is input to the 0-input terminal of the switch having theswitch address “01” in the malfunction stage (b), and output from the1-output terminal of the same switch. Thereafter, the communicationinformation is input to the 0-input terminal of the switch having theswitch address “11” in the malfunction stage (c), and output from the1-output terminal of the same switch. Finally, the communicationinformation is output from the output address “111” of the switchnetwork 1.

[0079] When the malfunctioning switch detecting unit 5 detects themalfunctioning switch, the selecting unit 11 refers to the input table(1) information stored in the input table (1) storing unit 7 since themalfunctioning switch is included in the malfunction stage (a) (thefirst stage). The input table (1) information provides the informationas shown in FIG. 6B. Accordingly, the control unit 2 refers to, as inputand output information, a case in which the input address is “000” andthe switch address “00” of the malfunctioning switch (indicated byhatched portion of FIG. 6B). In this case, an input address after changeindicates other than “*00”. This means that the selecting unit 11 shouldselect input addresses other than the input addresses “000” and “100” soas to change a transmission path to bypass the malfunctioning switch.Accordingly, for example, the malfunctioning switch can be bypassed ifthe routing information supplied to the input switching unit 3 ischanged to “001111”. It should be noted that the routing information isnot limited to “001111”.

[0080] A description will now be given, with reference to FIGS. 7A and7B, of an operation of the control unit 2 when the output table (1)information stored in the output table (1) storing unit 10 is referredto.

[0081]FIG. 7A shows a case in which a malfunction occurs in a switchhaving a switch address “11” in the malfunction stage (c). In the caseshown in FIG. 7A, an original routing information is “000111” whichindicates a transmission path routing from the input having the address“000” to the output having the address “111” (indicated by a bold solidline in FIG. 7A).

[0082] When the malfunctioning switch detecting unit 5 detects themalfunctioning switch, the selecting unit 11 refers to the output table(1) information stored in the output table (1) storing unit 10 since themalfunctioning switch is included in the malfunction stage (c) (thefinal stage). The output table (1) information provides the informationas shown in FIG. 7B. Accordingly, the control unit 2 refers to, as inputand output information, a case in which the output address is “111” andthe switch address “11” of the malfunctioning switch (indicated byhatched portion of FIG. 7B). In this case, an output address afterchange indicates other than “11*”. This means that the selecting unit 11should select output addresses other than the output addresses “111” and“110” so as to change a transmission path to bypass the malfunctioningswitch. Accordingly, for example, the malfunctioning switch can bebypassed if the routing information supplied to the input switching unit3 is changed to “000011”. It should be noted that the routinginformation is not limited to “000011”.

[0083] A description will now be given, with reference to FIGS. 8A and8B, of an operation of the control unit 2 when the input table (2)information stored in the input table (2) storing unit 8 is referred to.

[0084]FIG. 8A shows a case in which a malfunction occurs in a switchhaving a switch address “01” in the malfunction stage (b). In the caseshown in FIG. 7A, an original routing information is “000111” whichindicates a transmission path routing from the input having the address“000” to the output having the address “111” (indicated by a bold solidline in FIG. 8A).

[0085] When the malfunctioning switch detecting unit 5 detects themalfunctioning switch, the selecting unit 11 refers to the input table(2) information stored in the input table (2) storing unit 8 since themalfunctioning switch is included in the malfunction stage (b) (theintermediate stage). The information table (2) information provides theinformation as shown in FIG. 8B. Accordingly, the control unit 2 refersto, as input and output information, a case in which the input addressis “000” and the switch address “01” of the malfunctioning switch(indicated by hatched portion of FIG. 8B). In this case, an inputaddress after change indicates other than “**1”. This means that theselecting unit 11 should select input addresses other than the inputaddresses “000”, “010”, “100” and “110” so as to change a transmissionpath to bypass the malfunctioning switch. Accordingly, for example, themalfunctioning switch can be bypassed if the routing informationsupplied to the input switching unit 3 is changed to “001111”. It shouldbe noted that the routing information is not limited to “001111”.

[0086] A description will now be given, with reference to FIGS. 9A and9B, of an operation of the control unit 2 when the output table (2)information stored in the output table (2) storing unit 9 is referredto.

[0087]FIG. 9A shows a case in which a malfunction occurs in a switchhaving a switch address “01” in the malfunction stage (c). In the caseshown in FIG. 9A, an original routing information is “000111” whichindicates a transmission path routing from the input having the address“000” to the output having the address “111” (indicated by a bold solidline in FIG. 9A).

[0088] When the malfunctioning switch detecting unit 5 detects themalfunctioning switch, the selecting unit 11 refers to the output table(2) information stored in the output table (2) storing unit 9 since themalfunctioning switch is included in the malfunction stage (b) (theintermediate stage). The output table (2) information provides theinformation as shown in FIG. 9B. Accordingly, the control unit 2 refersto, as input and output information, a case in which the output addressis “111” and the switch address “01” of the malfunctioning switch(indicated by hatched portion of FIG. 9B). In this case, an outputaddress after change indicates other than “1**”. This means that theselecting unit 11 should select output addresses other than the outputaddresses “111”, “110”, “101” and “100” so as to change a transmissionpath to bypass the malfunctioning switch. Accordingly, for example, themalfunctioning switch can be bypassed if the routing informationsupplied to the input switching unit 3 is changed to “000011”. It shouldbe noted that the routing information is not limited to “000011”.

[0089]FIG. 10 is a block diagram of the input switching unit 3 shown inFIG. 4. In FIG. 10, the input switching unit 3 comprises a routinginformation changing unit 21, a final stage malfunction flag 22 and aswitch 23. The input switching unit 3 changes the routing informationcontained in the frame format of the communication information, when amalfunction occurs in the switch network 1, based on the input andoutput unit changing information and the final stage malfunction flagwhich are sent from the control unit 2.

[0090] The routing information changing unit 21 changes the contents ofa frame format (header) of the communication information, when amalfunction occurs in the switch network 1, based on the input andoutput unit changing information sent from the control unit 2. If themalfunctioning switch is included in the first stage, the routinginformation changing unit 21 changes the input address. If themalfunctioning switch is included in the final stage, the routinginformation changing unit 21 changes the output address. If themalfunctioning switch is included in the intermediate stage, the routinginformation changing unit 21 changes one of the input address and theoutput address.

[0091] The final stage malfunction flag changing unit 22 changes thestatus of the final stage malfunction flag contained in the frame formatof the communication information, when a malfunction occurs in theswitch network 1, based on the final stage malfunction flag sent fromthe control unit 2. When the malfunctioning switch is included in thefinal stage of the switch network 1 or when the malfunctioning switch isincluded in the intermediate stage of the switch network 1 and theoutput address is to be changed, the final stage malfunction flagchanging unit 22 sets the final stage malfunction flag to “1”.

[0092] The switch 23 changes an input direction of the communicationinformation based on the changed frame format of the communicationinformation when the malfunctioning switch is included in the firststage of the switch network 1 or when the malfunctioning switch isincluded in the intermediate stage and the input address is to bechanged.

[0093]FIG. 11 is a block diagram of the output switching unit 4 shown inFIG. 4. In FIG. 11, the output switching unit 4 comprises a final stagemalfunction flag determining unit 31 and a switch 32. The outputswitching unit 4 switches an outputting direction of the communicationinformation to be sent to one of the output addresses, when amalfunction occurs in the switch network 1, based on the input andoutput unit changing information and the final stage malfunction flagwhich are sent from the control unit 2.

[0094] The final stage malfunction flag determining unit 31 determinesthe status of the final stage malfunction flag contained in the frameformat of the communication information. When a result of thedetermination of the final stage malfunction flag determining unit 31indicates “ON”, the switch 32 changes the output address based on therouting information contained in the frame format of the communicationinformation.

[0095]FIGS. 12A is an illustration for explaining a change in the frameformat made by the input switching unit 3 shown in FIG. 10 when amalfunction occurs in one of the switches included in the first stage asis in the case shown in FIG. 6A. FIG. 12B is an illustration forexplaining a change in the frame format made by the output switchingunit 4 shown in FIG. 11 when a malfunction occurs in one of the switchesincluded in the first stage as is in the case shown in FIG. 6A. Itshould be noted that a change of the frame format when themalfunctioning switch is included in the intermediate stage and theinput address is to be changed is the same as that of the case in whichthe malfunctioning switch is included in the first stage of the switchnetwork 1.

[0096] In FIG. 12A, when the frame format (routing information beforechange “000111”, a final stage malfunction flag “OFF”) of thecommunication information is input to the input address “000” of theinput switching unit 3, the routing information changing unit 21 changesthe routing information to, “001111”, for example, based on the inputand output unit changing information produced by the control unit 2 asis in the case shown in FIGS. 6A and 6B. At this time, the routinginformation before change is maintained.

[0097] When the routing information is changed to “001111”, the inputaddress in the frame format of the communication information is changedfrom “000” to “001” by the switch 23. The communication informationinput to the input address “001” of the switch network 1 is output fromthe output address “111” of the switch network 1.

[0098] As shown in FIG. 12B, the frame format of the communicationinformation output from the output address “111” of the switch network 1is output to the output address “111” of the output switching unit 4 viathe final stage malfunction flag determining unit 31 and the switch 32while the present information is also maintained.

[0099]FIGS. 13A is an illustration for explaining a change in the frameformat made by the input switching unit 3 shown in FIG. 10 when amalfunction occurs in one of the switches included in the final stage asis in the case shown in FIG. 7A. FIG. 13B is an illustration forexplaining a change in the frame format made by the output switchingunit 4 shown in FIG. 11 when a malfunction occurs in one of the switchesincluded in the final stage as is in the case shown in FIG. 7A. Itshould be noted that a change in the frame format when themalfunctioning switch is included in the intermediate stage and theoutput address is to be changed is the same as that of the case in whichthe malfunctioning switch is included in the final stage of the switchnetwork 1.

[0100] In FIG. 13A, when the frame format (routing information beforechange “000111”, a final stage malfunction flag “OFF”) of thecommunication information is input to the input address “000” of theinput switching unit 3, the routing information changing unit 21 changesthe routing information to “000011”, for example, based on the input andoutput unit changing information produced by the control unit 2 as is inthe case shown in FIGS. 7A and 7B. At this time, the routing informationbefore change is maintained.

[0101] When the routing information is changed to “000011”, the statusof the final stage malfunction flag is changed to “ON” by the finalstage malfunction flag changing unit 22. Additionally, the input address“000” is output to the switch network 1 via the switch 23. Thus, thecommunication information input to the input address “000” of the switchnetwork 1 is output from the output address “011” of the switch network1.

[0102] As shown in FIG. 13B, the frame format of the communicationinformation output from the output address “011” of the switch network 1is output to the output address “111” of the output switching unit 4after the status of the final stage malfunction flag is determined bythe final stage malfunction flag determining unit 31 and changed to therouting information before change “111” while the present information isalso maintained.

[0103]FIG. 14 is a flowchart of an operation of the exchange accordingto the present embodiment when the exchange is in a normal condition orwhen a malfunction occurs in the switch network 1 as shown in FIGS. 15Aand 15B, 16A and 16B, 17A and 17B, and 18A and 18B. In the operationshown in FIG. 14, it is assumed that the communication informationhaving routing information “000111” in the frame format is input, instep S1, to the input address “000” of the input switching unit 3 whenthe exchange is normally operated. The communication information isinput to the input address “000” of the switch network 1 as shown inFIGS. 15A, 16A, 17A and 18A via the routing information changing unit21, the final stage malfunction flag changing unit 22 and the switch 23in the input switching unit 3.

[0104] Then, in step S2, a routing from the input address “000” to theoutput address “111” is performed. Each of the switches included in theswitch network 1 has the 0-input terminal, 1-input terminal, 0-outputterminal and the 1-output terminal as shown in FIG. 6C. Each digit ofthe input address “000” corresponds to the input terminal of each of theswitches in the respective stages (a), (b) and (c). Each digit of theoutput address “111” corresponds to the output terminal of each of theswitches in the respective stages (a), (b) and (c). Specifically, asshown in FIG. 15A, the communication information input to the inputaddress “000” of the switch network 1 is input to the 0-input terminalof the switch having the switch address “00” in the stage (a), and isoutput from 1-output terminal of the same switch. The communicationinformation is then input to the 0-input terminal of the switch havingthe switch address “01” in the stage (b), and is output from the1-output terminal of the same switch. After that, the communicationinformation is input to the 0-input terminal of the switch having theswitch address “11” in the stage (c), and is output from the 1-outputterminal of the same switch. Finally, the communication information isoutput from the output address “111” of the switch network 1.

[0105] The communication information output from the switch network 1 isinput to the input address “111” of the output switching unit 4. In stepS3, the final stage malfunction flag determining unit 31 of the outputswitching unit 4 determines whether the final stage malfunction flag is“ON” or “OFF”. In this case, since the switch network 1 is normallyoperating, it is determined that the final stage malfunction flag is“OFF”. Thus, the communication information is output, in step S4, to theoutput address “111” of the output switching unit 4 via the switch 32.

[0106] On the other hand, when a malfunction occurs in one of theswitches in the switch network 1 in step S11, the exchange according tothe present embodiment detects, in step S12, the location of themalfunctioning switch by the malfunctioning switch detecting unit 5.

[0107] If the switch address “00” in the stage (a) (the first stage) isdetected by the malfunction detecting unit 5 as the location of themalfunctioning switch, the selecting unit 11 refers to the input table(1) information stored in the input table (1) storing unit 7 in stepS13. The input table (1) information provides, for example, theinformation shown in FIG. 6B, and the selecting unit 11 refers to the“input address after change” in a case in which the input address of theswitch network 1 is “000” and the address of the malfunctioning switchis “00” (indicated by hatched portions in FIG. 6B). Thus, the selectingunit 11 selects, in step S14, a transmission path which routes from oneof the input addresses other than the input addresses “000” and “100” tothe output address “111” so as to bypass the malfunctioning switch.Accordingly, the selecting unit 11 sends to the input switching unit 3the input and output unit changing information which provides aninstruction to change the routing information to “001111”, for example.It should be noted that the routing information to be set is not limitedto “001111”.

[0108] When the communication information having the routing information“001111” in the frame format is input to the input address “000” of theinput switching unit 3, the routing information changing unit 21 of theinput switching unit 3 changes the routing information to “001111”, instep S15, based on the input and output unit changing informationproduced by the selecting unit 11.

[0109] After the routing information in the frame format of thecommunication information is changed to “001111”, the communicationinformation is passed through the final stage malfunction flag changingunit 22. Thereafter, the switch 23 changes, in step S16, the inputaddress of the switch network 1, to which the communication informationis input, from “000” to “001”. Thus, the communication information isoutput from the switch 23 to the input address “001” of the switchnetwork 1.

[0110] Then, in step S2, a routing from the input address “001” to theoutput address “111” is performed. Each digit of the input address “001”corresponds to the input terminal of each of the switches in therespective stages (a), (b) and (c). Each digit of the output address“111” corresponds to the output terminal of each of the switches in therespective stages (a), (b) and (c). Specifically, as shown in FIG. 15B,the communication information input to the input address “001” of theswitch network 1 is input to the 0-input terminal of the switch havingthe switch address “00” in the stage (a), and is output from 1-outputterminal of the same switch. The communication information is then inputto the 0-input terminal of the switch having the switch address “11” inthe stage (b), and is output from the 1-output terminal of the sameswitch. After that, the communication information is input to the0-input terminal of the switch having the switch address “11” in thestage (c), and is output from the 1-output terminal of the same switch.Finally, the communication information is output from the output address“111” of the switch network 1.

[0111] The communication information output from the switch network 1 isinput to the input address “111” of the output switching unit 4. In stepS3, the final stage malfunction flag determining unit 31 of the outputswitching unit 4 determines whether the final stage malfunction flag is“ON” or “OFF”. In this case, since the malfunctioning switch is includedin the first stage, it is determined that the final stage malfunctionflag is “OFF”. Thus, the communication information is output, in stepS4, to the output address “111” of the output switching unit 4 via theswitch 32.

[0112] In the process of step S12, if the switch address “11” in thestage (c) (the final stage) is detected by the malfunction detectingunit 5 as the location of the malfunctioning switch as shown in FIG.16A, the selecting unit 11 refers to the output table (1) informationstored in the output table (1) storing unit 10 in step S17. The outputtable (1) information provides, for example, the information shown inFIG. 7B, and the selecting unit 11 refers to the “output address afterchange” in a case in which the output address of the switch network 1 is“*11” and the address of the malfunctioning switch is “11” (indicated byhatched portions in FIG. 7B). Thus, the selecting unit 11 selects, instep S18, a transmission path which is connected to output addressesother than the output addresses “111” and “110” so as to bypass themalfunctioning switch. Accordingly, the selecting unit 11 sends to theinput switching unit 3 the input and output unit changing informationwhich instructs to change the routing information to “001111”, forexample. It should be noted that the routing information to be set isnot limited to “001111”.

[0113] When the communication information having the routing information“001111” in the frame format is input to the input address “000” of theinput switching unit 3, the routing information changing unit 21 of theinput switching unit 3 changes the routing information to “001111”, instep S19, based on the input and output unit changing informationproduced by the selecting unit 11.

[0114] After the routing information in the frame format of thecommunication information is changed to “001111”, the final stagemalfunction flag changing unit 22 changes, in step S19, the final stagemalfunction flag to “ON” and the communication information is output tothe input address “000” of the switch network 1 via the switch 23.

[0115] Then, in step S2, a routing from the input address “001” to theoutput address “111” is performed in the switch network 1.

[0116] Each digit of the input address “000”corresponds to the inputterminal of each of the switches in the respective stages (a), (b) and(c). Each digit of the output address “011” corresponds to the outputterminal of each of the switches in the respective stages (a), (b) and(c). Specifically, as shown in FIG. 16B, the communication informationinput to the input address “000” of the switch network 1 is input to the0-input terminal of the switch having the switch address “00” in thestage (a), and is output from the 0-output terminal of the same switch.The communication information is then input to the 0-input terminal ofthe switch having the switch address “00” in the stage (b), and isoutput from the 1-output terminal of the same switch. After that, thecommunication information is input to the 0-input terminal of the switchhaving the switch address “01” in the stage (c), and is output from the1-output terminal of the same switch. Finally, the communicationinformation is output from the output address “011” of the switchnetwork 1.

[0117] The communication information output from the switch network 1 isinput to the input address “011” of the output switching unit 4. In stepS3, the final stage malfunction flag determining unit 31 of the outputswitching unit 4 determines whether the final stage malfunction flag is“ON” or “OFF”. In this case, since the malfunctioning switch is includedin the final stage, it is determined that the final stage malfunctionflag is “ON”. Thus, the switch 32 changes, in step 5, the output addressto which the communication information is output to the original outputaddress “111”, and the communication information is output to the outputaddress “111” of the output switching unit 4 via the switch 32. Sincethe switching operation of the output switching unit 4 can be performedbased on the determination by the final stage malfunction flagdetermining unit 31 as to whether the final stage malfunction flag is“ON” or “OFF”, the output switching unit 4 can perform the switching ofthe output address without a direct instruction from the control unit 2.

[0118] In the process of step S12, if the switch address “01” in thestage (b) (the intermediate stage) is detected by the malfunctiondetecting unit 5 as the location of the malfunctioning switch as shownin FIG. 17A and if an instruction is provided to change the inputaddress so as to bypass the malfunctioning switch when themalfunctioning switch is located in the intermediate stage of the switchnetwork 1, the selecting unit 11 refers to the input table (2)information stored in the input table (2) storing unit 8 in step S20.

[0119] The input table (2) information provides, for example, theinformation shown in FIG. 8B, and the selecting unit 11 refers to the“input address after change” in a case in which the input address of theswitch network 1 is “000” and the address of the malfunctioning switchis “01” (indicated by hatched portions in FIG. 8B). Thus, the selectingunit 11 selects, in step S22, a transmission path routing from an inputaddress other than the input addresses “000”, “010”, “100” and “110” tothe output address “111” so as to bypass the malfunctioning switch.Accordingly, the selecting unit 11 sends to the input switching unit 3the input and output unit changing information which instructs to changethe routing information to “001111”, for example. It should be notedthat the routing information to be set is not limited to “001111”.

[0120] When the communication information having the routing information“001111” in the frame format is input to the input address “000” of theinput switching unit 3, the routing information changing unit 21 of theinput switching unit 3 changes the routing information to “001111”, instep S23, based on the input and output unit changing informationproduced by the selecting unit 11.

[0121] After the routing information in the frame format of thecommunication information is changed to “001111”, the communicationinformation is passed through the final stage malfunction flag changingunit 22. Thereafter, the final stage malfunction flag changing unit 22changes, in step S24, the input address of the switch network 1, towhich the communication information is input, from “000” to “001”. Thus,the communication information is output from the switch 23 to the inputaddress “001” of the switch network 1.

[0122] Then, in step S2, a routing from the input address “001” to theoutput address “111” is performed in the switch network 1.

[0123] Each digit of the input address “001” corresponds to the inputterminal of each of the switches in the respective stages (a), (b) and(c). Each digit of the output address “111” corresponds to the outputterminal of each of the switches in the respective stages (a), (b) and(c). Specifically, as shown in FIG. 17B, the communication informationinput to the input address “000” of the switch network 1 is input to the0-input terminal of the switch having the switch address “00” in thestage (a), and is output from 1-output terminal of the same switch. Thecommunication information is then input to the 0-input terminal of theswitch having the switch address “01” in the stage (b), and is outputfrom the 1-output terminal of the same switch. After that, thecommunication information is input to the 0-input terminal of the switchhaving the switch address “11” in the stage (c), and is output from the1-output terminal of the same switch. Finally, the communicationinformation is output from the output address “111” of the switchnetwork 1.

[0124] The communication information output from the switch network 1 isinput to the input address “111” of the output switching unit 4. In stepS3, the final stage malfunction flag determining unit 31 of the outputswitching unit 4 determines whether the final stage malfunction flag is“ON” or “OFF”. In this case, since the instruction is provided so as tochange the input address when a malfunction occurs in one of theswitches in the intermediate stage, it is determined that the finalstage malfunction flag is “OFF”. Thus, the communication information isoutput, in step S4, to the output address “111” of the output switchingunit 4 via the switch 32.

[0125] In the process of step S12, if the switch address “11” in thestage (c) (the final stage) is detected by the malfunction detectingunit 5 as the location of the malfunctioning switch as shown in FIG. 18Aand if an instruction is provided so as to change the output address ofthe switch network 1 when a malfunction occurs in one of the switches inthe intermediate stage, the selecting unit 11 refers to the output table(2) information stored in the output table (2) storing unit 9 in stepS21. The output table (1) information provides, for example, theinformation shown in FIG. 9B, and the selecting unit 11 refers to the“output address after change” in a case in which the output address ofthe switch network 1 is “111” and the address of the malfunctioningswitch is “01” (indicated by hatched portions in FIG. 9B). Thus, theselecting unit 11 selects, in step S22, a transmission path which isconnected to an output address other than the output addresses “111”,“110”, “101 and “100” so as to bypass the malfunctioning switch.Accordingly, the selecting unit 11 sends to the input switching unit 3the input and output unit changing information which provides aninstruction to change the routing information to “000011”, for example.It should be noted that the routing information to be set is not limitedto “000011”.

[0126] When the communication information having the routing information“000011” in the frame format is input to the input address “000” of theinput switching unit 3, the routing information changing unit 21 of theinput switching unit 3 changes the routing information to “000011”, instep S23, based on the input and output unit changing informationproduced by the selecting unit 11.

[0127] After the routing information in the frame format of thecommunication information is changed to “000011”, the final stagemalfunction flag changing unit 22 changes, in step S23, the final stagemalfunction flag to “ON” and the communication information is output tothe input address “000” of the switch network 1 via the switch 23.

[0128] Then, in step S2, a routing from the input address “000” to theoutput address “011” is performed in the switch network 1.

[0129] Each digit of the input address “000” corresponds to the inputterminal of each of the switches in the respective stages (a), (b) and(c). Each digit of the output address “011” corresponds to the outputterminal of each of the switches in the respective stages (a), (b) and(c). Specifically, as shown in FIG. 18B, the communication informationinput to the input address “000” of the switch network 1 is input to the0-input terminal of the switch having the switch address “00” in thestage (a), and is output from the 0-output terminal of the same switch.The communication information is then input to the 0-input terminal ofthe switch having the switch address “00” in the stage (b), and isoutput from the 1-output terminal of the same switch. After that, thecommunication information is input to the 0-input terminal of the switchhaving the switch address “01” in the stage (c), and is output from the1-output terminal of the same switch. Finally, the communicationinformation is output from the output address “011” of the switchnetwork 1.

[0130] The communication information output from the switch network 1 isinput to the input address “011” of the output switching unit 4. In stepS3, the final stage malfunction flag determining unit 31 of the outputswitching unit 4 determines whether the final stage malfunction flag is“ON” or “OFF”. In this case, since the instruction is provided so as tochange the output address of the switch network 1 when a malfunctionoccurs in one of the switches in the intermediate switch, it isdetermined that the final stage malfunction flag is “ON”. Thus, theswitch 32 changes, in step 5, the output address, to which thecommunication information is output, to the original output address“111”, and the communication information is output to the output address“111” of the output switching unit 4 via the switch 32. Since theswitching operation of the output switching unit 4 can be performedbased on the determination by the final stage malfunction flagdetermining unit 31 as to whether the final stage malfunction flag is“ON” or “OFF” by the, the output switching unit 4 can perform theswitching of the output address without a direct instruction from thecontrol unit 2.

[0131] As mentioned above, according to the exchange of the presentembodiment, when a malfunction occurs in the switch network 1 in which atransmission path is formed to transmit the communication information,only the transmission path including the malfunctioning switch ischanged so as to bypass the malfunctioning switch. Thus, the exchangeaccording to the present embodiment does not have spare switches whichwould cause an increase in the weight and size of the entire system.

[0132] The present invention is not limited to the specificallydisclosed embodiments, and variations and modifications may be madewithout departing from the scope of the present invention.

What is claimed is:
 1. An exchange setting a transmission path fortransmitting communication information through a switch networkcomprising a plurality of switches, said switch network provided with aplurality of inputs and a plurality of outputs so that the transmissionpath is formed between one of the inputs and one of the outputs byrouting the switches in said switch network, said exchange changing aroute of the transmission path when a malfunction occurs in one of theswitches included in the transmission path so as to bypass themalfunctioning switch, said exchange comprising: a malfunctioning switchdetecting unit detecting a location of the malfunctioning switch in saidswitch network; and changing means for changing the route of thetransmission path by switching one of the inputs and outputs connectedto the transmission path based on predetermined routing information soas to bypass the malfunctioning switch.
 2. The exchange as claimed inclaim 1, wherein said changing means comprises: a storing unit whichstores table information indicating a plurality of routes each of whichbypasses one of the switches in said switch network, each of the routesbeing indicated in relation to one of the inputs and outputs of theswitch network; and a selecting unit selecting one of the routesindicated in said table information so as to change the route of thetransmission path to bypass the malfunctioning switch.
 3. The exchangeas claimed in claim 2, wherein said changing means further comprises: aninput switching unit switching the input of said switch network; anoutput switching means switching the output of said switch network; andinput and output selecting means for selecting one of said inputswitching unit and said output switching unit so that said changingmeans changes the route of the transmission path by the selected one ofsaid input switching unit and said output switching unit.
 4. Theexchange as claimed in claim 3, wherein said input and output selectingmeans selects said input switching unit when the malfunctioning switchis one of the switches directly connected to said input switching unit.5. The exchange as claimed in claim 3, wherein said input and outputselecting means selects said output switching unit when themalfunctioning switch is one of the switches directly connected to saidoutput switching unit.
 6. The exchange as claimed in claim 3, whereinsaid input and output selecting means selects said input switching unitwhen the malfunctioning switch is one of the switches other than theswitches directly connected to one of said input switching unit and saidoutput switching unit.
 7. The exchange as claimed in claim 3, whereinsaid input and output selecting means selects said output switching unitwhen the malfunctioning switch is one of the switches other than theswitches directly connected to one of said input switching unit and saidoutput switching unit.